Something astonishing is happening to the market for young, smart labor. The luster of big prestigious firms, particularly on Wall Street, has dimmed: "The End of Wall Street as They Knew It," goes a recent New York Magazine headline. A few months ago at Davos, CEOs complained about the brain drain affecting their companies. Where are all these people going? Increasingly to start-ups, which seem to have captured the public imagination, particularly among millennials (ages 18 to 29). In an opinio